Aethelgard Ledger

A double-entry, multi-entity, tamper-evident ledger for AI agents.

Aethelgard Ledger is a local Model Context Protocol server. It gives your agent real accounting tools backed by an engine that enforces accounting rules. The agent can't talk its way past them. It is the same engine that runs the Aethelgard desktop ledger.

Evaluation build, for business use only. Licensed under the Aethelgard Ledger Evaluation Licence. The ledger file is not encrypted, and output must not be relied on without independent verification.

What it does

Balanced journals or nothing. Every posting must balance. If debits don't equal credits, the engine rejects the posting and returns the reason, so the agent can't book it.
Multi-entity. Companies, trusts and individuals across 9 jurisdictions, with subsidiaries linked to a parent and a combined group trial balance. This is a straight sum by account code, not a full consolidation; eliminations live in the Aethelgard desktop app.
Tamper-evident. Every posting is linked into a per-entity SHA-256 hash-chain, so an entry edited outside the engine fails the integrity check. The chain is unkeyed. For independent assurance, record the latest chain hash (returned by verify_integrity) somewhere outside the ledger and compare it later.
Local. The ledger lives in a file on your machine and is never sent to us.

Tools

Tool	What it does
`create_entity`	Create a company, trust or individual, optionally as a subsidiary of a parent
`create_account`	Add an account (ASSET, LIABILITY, EQUITY, REVENUE, EXPENSE)
`post_transaction`	Post a double-entry journal; unbalanced journals are rejected
`list_entities`	List entities
`list_accounts`	List an entity's chart of accounts
`list_transactions`	List postings with every journal line, filtered by date
`trial_balance`	Trial balance for one entity
`consolidate`	Combined trial balance for a parent and its direct subsidiaries, summed by account code (no intercompany eliminations)
`verify_integrity`	Verify the hash-chain and return the latest chain hash

Download

Get the latest build from Releases.

Platform	File	Signing
Windows (x86_64)	`aethelgard-mcp-<version>-windows-x86_64.zip`	Signed by Aethelgard Finance Ltd
macOS (Intel + Apple Silicon)	`aethelgard-mcp-<version>-macos-universal.zip`	Developer ID signed and notarized by Apple
Linux (x86_64, static)	`aethelgard-mcp-<version>-linux-x86_64.tar.gz`	Verify with `SHA256SUMS`

Quick start

Unzip it and put aethelgard-mcp somewhere permanent. Check it runs: aethelgard-mcp --version.
Add it to your MCP client as a local (stdio) server.

Claude Code
Terminal
```
claude mcp add aethelgard-ledger -- /full/path/to/aethelgard-mcp
```
Claude Desktop, Cursor and other clients
config.json
```
{
  "mcpServers": {
    "aethelgard-ledger": { "command": "/full/path/to/aethelgard-mcp" }
  }
}
```
On Windows, use the path to aethelgard-mcp.exe with doubled backslashes, e.g. "C:\\Tools\\aethelgard-mcp.exe".
Ask your agent to keep some books. For example: "Create PropCo Ltd (GBP, GB, UkLtd) with a bank and a rental income account, then post October's £1,500 rent."

Where the ledger is kept

Platform	Default location
Windows	`%APPDATA%\Aethelgard Ledger`
macOS	`~/Library/Application Support/Aethelgard Ledger`
Linux	`~/.local/share/aethelgard-ledger`

To keep it somewhere else, use --vault <DIR> or set AETHELGARD_LEDGER_VAULT. Use --ephemeral for a throwaway ledger that is deleted when the server stops. Run aethelgard-mcp --help for every option.

Your data

The server runs on your machine and does not send your ledger to us. There is no telemetry. Your MCP client and the AI model you connect see whatever the tools return, such as balances and transactions, under that provider's terms. Choose them accordingly.

Licence

Aethelgard Ledger Evaluation Licence, which covers free evaluation and internal pilots for business use. Open-source components are listed with their licences in THIRD-PARTY-NOTICES.txt inside each download. Production or commercial use needs a separate licence.

This repository contains documentation and releases only. The software is closed source.

Contact

Feedback, bugs and commercial licensing: contact@aethelgard.finance. Bug reports are welcome as issues.